The contacts of electromechanical devices on ship electrical system are utilized through control circuitry only are unlikely to sustain currents higher than 10 Amps. They are called control relays, but are also referred to as relays.
Relays are used to controlling and regulate circuits for the indirect control of electric motors, valves and clutches.
A modular system is formed around functional basic units, consisting of an AC or DC operated drive (coil with armature) and auxiliary contacts.
The control relay’s basic unit consists of four contact blocks (poles) marked with reference numbers:
• 13-14 (NO contact)
• 21-22 (NC contact)
• 33-34 (NO contact)
• 43-44 (NO contact).
Reference numbers are also shown as a table in most control diagrams, usually below the relay’s coil symbol.
The manufacturer’s stamp should be marked on the unit and reference letters marked adjacent to the terminals (53NO, 61A/C, 75NC, 87A/0).These manufacturer’s numbers are an important reference for reordering or cross-ordering with other manufacturers components.
